The present invention involves an improved apparatus and method for cleaning surfaces and crevices of teeth. The purpose of this cleaning is to remove dental plaque which indirectly gives rise to both caries and periodontal disease.
In the prior art, apparatus and methods for brushing teeth are generally divided into three broad categories. The first consists of non-powered brushes in which a number of tufts composed of individual bristles are anchored in a brush head and the movement of the bristles with respect to the teeth is accomplished by physically moving the brush head by hand. The second consists of powered brushes in which the brush head, composed of tufts and bristles similar to those used in hand brushes, is moved in rotary, arcuate, reciprocating, or orbital paths by the power mechanism and in larger paths by hand movement. The third consists of powered brushes in which the brush head is substantially stationary and individual tufts are mechanically rotated unidirectionally each along its own axis.
With conventional hand brush practices, when surface areas and crevices of teeth are involved, cleaning of the smooth facial and lingual surfaces of the teeth is relatively easy because the tips of the bristles in a tuft move with little or no restriction across these broad areas or surfaces. However, approximately ninety percent of the incidence of caries and seventy percent of the incidence of periodontal disease occurs in the interproximal crevices along the mesial and distal surfaces, or the pits and fissures of the occlusal surfaces. In cleaning these areas, the tips of the bristles generally pass over these indentations or recesses. If the bristles are forced into the indentations, they tend to wedge against each other because of their flexibility and length, and assume a static posture which is relatively inefficient for removal of adhesive dental plaque from the indentations. Wedging of the bristles in the indented or recessed areas, as noted above, is due to the fact that the bristles of the tufts are relatively long and flexible. Furthermore, the characteristic flexibility of the individual bristles physically defines a structure which is capable of transmitting to the bristle tips only a very small portion of the motion or power generated at the anchor position of the bristles with the brush head.
Powered brushes of the second category set forth above, such as disclosed in U.S. Pat. No. 3,577,579 issued to Duve et al., are not as effective as the apparatus and method of the present invention because the powered brushes use brush structures similar to conventional hand brushes. In other words, these powered brushes typically do not overcome the disadvantages of the brush structures, including wedging of the bristles and ineffective transmission of power from the brush head to the bristle tips.
Powered toothbrush apparatus of the third category, such as the power driven toothbrush disclosed in U.S. Pat. No. 2,215,031 issued to N. Elmore, generally include means for rotating each of the individual tufts of the brush head continuously in one direction. Because of this unidirectional rotation, the individual tufts of these bristles easily "run-out" of crevices between large surfaces of teeth. This phenomenon is analgous to the characteristic "running-out" of a conventional power drill bit when it is either placed in an irregularly shaped starting opening, or tilted at an angle not normal to the surface to be drilled. In the mouth, the interproximal crevices are irregularly shaped openings, and it is difficult to insert the tufts of a straight-headed brush into the crevices at right angles due to the curvature of the dental arch. This tendency to move out of a crevice or indentation impairs the cleaning efficiency of the toothbrush because the tuft is difficult to position within a crevice for an amount of time adequate to achieve removal of foreign matter desposited within the crevice.